Transforming maritime CO2 emissions into solid materials through innovative carbon capture technology
Imagine a massive container ship, longer than three football fields, crossing the ocean while effectively scrubbing carbon dioxide from its own exhaust. This isn't science fiction—it's rapidly becoming maritime reality.
The global shipping industry, responsible for approximately one billion tons of CO2 annually (nearly 3% of worldwide emissions) 8 , is undergoing a quiet revolution in how it addresses its carbon footprint. While alternative fuels like green ammonia and methanol grab headlines, a more immediate solution is emerging directly onboard vessels: carbon capture and storage technology.
The concept is as ambitious as it is essential: instead of releasing CO2 into the atmosphere, ships can now capture, process, and store it right onboard. Through fascinating chemical processes, this captured carbon can even be transformed into solid materials—effectively turning greenhouse gases into stone. This technology represents a promising bridge in maritime decarbonization, allowing existing vessels to dramatically reduce emissions while the industry transitions to cleaner fuels over time.
At its core, onboard carbon capture and storage (OCCS) applies technology traditionally used in industrial settings to the unique environment of a ship.
CO2 is separated from exhaust gases using specialized solvents or membranes
CO2 is compressed and cooled into a liquefied state (LCO₂) for efficient storage
Liquefied CO2 is transformed into stable solid compounds for storage
The process begins at the vessel's exhaust systems, where emissions are diverted rather than released into the atmosphere. The captured CO2 then undergoes a remarkable transformation through several sophisticated stages:
The capture phase employs specialized solvents, membranes, or other separation technologies to isolate CO2 from other exhaust gases. This is no small feat on a moving vessel where space is limited and conditions constantly change. Once separated, the carbon dioxide moves to the processing phase, where it's compressed and cooled into a liquefied state (LCO₂) for efficient storage—a process requiring precise temperature and pressure control to prevent the formation of dry ice, which could damage equipment 3 .
The final stage offers perhaps the most innovative possibilities: solidification and storage. Through various chemical processes, the liquefied CO2 can be transformed into stable solid compounds. These solid carbonates take up significantly less space than gaseous or liquid CO2 and can be safely stored onboard until the ship reaches port, where they're offloaded for permanent storage or industrial use.
| System/Project | Capture Rate | CO2 Purity | Storage Method | Key Features |
|---|---|---|---|---|
| Wärtsilä CCS (Clipper Eris) | Up to 70% reduction in vessel CO2 emissions 1 | Not specified | Liquid CO2 in deck tanks 9 | Commercially available; works with various fuels including HFO, LNG, methanol 1 |
| SMDERI-QET System (EVER TOP) | 80% capture rate 8 | 99.9% purity 8 | Liquefied CO2, transferred ship-to-ship 8 | Ultra-high purity suitable for industrial applications; demonstrated commercial transfer |
| NYK LCO₂-EP System | Designed for transport, not capture | N/A (transport system) | Elevated Pressure method using slender cylinder tanks 3 | Proprietary technology for efficient CO2 transport; received Class NK approval |
In June 2025, at Shanghai's Yangshan Deepwater Port, maritime history was made.
The 14,000-TEU container vessel successfully completed the world's first ship-to-ship transfer of liquid carbon dioxide, offloading 25.44 metric tons of captured emissions directly to the barge Dejin while docked at the Shengdong Terminal 8 .
This operation represented far more than a technical achievement—it demonstrated a practical approach to maritime carbon capture that transforms captured emissions into a commercially viable commodity.
The landmark operation followed a meticulously planned procedure that could set the standard for future maritime carbon transfer:
During the EVER TOP's voyage, the OCCS system developed by Shanghai Marine Diesel Engine Research Institute (SMDERI) and QET continuously intercepted exhaust gases from the vessel's main engine and auxiliary systems. The system processed these emissions through a multi-stage capture and purification process.
The captured CO2 underwent immediate liquefaction onboard—a crucial step that eliminated the need for specialized shore-based facilities and enabled flexible transfer operations. The system maintained precise temperature and pressure conditions to ensure the CO2 remained in liquid form without solidifying into dry ice.
The EVER TOP established secure alongside positioning with the Dejin barge, following established maritime protocols adapted specifically for CO2 handling.
Crews connected specialized transfer hoses designed specifically for cryogenic liquid CO2 between the two vessels. These hoses incorporated safety systems to monitor pressure, temperature, and flow rates throughout the operation.
The liquid CO2 was transferred from the EVER TOP's storage tanks to the Dejin barge, with automated monitoring systems providing real-time data and capable of initiating automatic shutdown in case of anomalies.
Upon completion, the transfer hoses were safely disconnected, and the exact amount of transferred CO2—25.44 metric tons—was verified and documented.
The Shanghai demonstration achieved remarkable technical success, with the OCCS system maintaining an 80% capture rate while producing CO2 of 99.9% purity—a quality level that makes it suitable for premium industrial applications, including food processing and pharmaceutical manufacturing 8 . The entire transfer operation was conducted safely and efficiently alongside normal vessel operations, proving that carbon capture need not disrupt commercial shipping activities.
Perhaps most significantly, the operation prompted a crucial regulatory breakthrough: the reclassification of captured CO2 from hazardous waste to hazardous cargo 8 . This distinction, while seemingly subtle, transforms captured carbon from a disposal problem into a commercial commodity, creating potential revenue streams that could accelerate technology adoption across the global fleet.
| Performance Metric | Result | Significance |
|---|---|---|
| CO2 Transferred | 25.44 metric tons 8 | Proof of concept for commercial-scale operations |
| Capture Rate | 80% 8 | Among most efficient maritime carbon capture systems demonstrated |
| CO2 Purity | 99.9% 8 | Suitable for high-value industrial applications including food and pharmaceutical uses |
| System Cost | Approximately $10 million per vessel retrofit 8 | Less than half the cost of alternative fuel conversions |
| Transfer Method | Ship-to-ship while alongside 8 | Eliminates need for specialized shore infrastructure |
Transforming captured carbon dioxide into solid form involves several innovative approaches and specialized materials.
The process of mineralization—converting CO2 into stable carbonate rocks—has emerged as particularly promising for maritime applications because of its safety and permanence.
Industrial by-products such as steel slag or fly ash from power generation serve as ideal reactants for carbonation. These materials contain calcium and magnesium oxides that naturally react with CO2 to form stable carbonates. Their availability in port cities creates potential for symbiotic relationships between shipping and industrial operations 8 .
Onboard ships, specialized reactors create optimal conditions for rapid carbonation. These systems control temperature, pressure, and mixing to accelerate reactions that would normally take years in nature to occur in hours or days. The compact design of these reactors makes them suitable for the space-constrained environment of commercial vessels.
Researchers are exploring how seawater's natural mineral content can be harnessed to facilitate carbonation processes. The magnesium and calcium naturally present in seawater offer potential pathways for direct ocean carbon capture that could be integrated with shipboard systems.
Once solidified, the carbonate materials require specialized storage solutions onboard. Engineers have developed compact, modular storage containers that can be easily loaded and unloaded using standard port infrastructure. The solid form eliminates risks associated with liquefied gas storage, such as pressure management and temperature control.
Beyond simple storage, solid carbonates have commercial value in various industries. They can be used as construction materials, additives in cement production, or soil amendments in agriculture. This creates the potential for ships to not only reduce emissions but generate additional revenue streams from their captured carbon.
| Material/Process | Function | Application in Maritime Context |
|---|---|---|
| Steel Slag | Source of calcium and magnesium oxides for carbonation 8 | Reactant for solid carbonate production; potential synergy with port industries |
| Fly Ash | Industrial byproduct containing reactive oxides | Carbonation reactant; utilization of waste materials |
| Seawater Minerals | Natural source of magnesium and calcium | Potential catalyst for ocean-based carbonation processes |
| Specialized Reactors | Controlled environment for accelerated carbonation | Onboard systems for solid carbonate production |
| Modular Solid Storage | Safe containment of carbonate products | Efficient onboard storage using standard container technology |
While the technical feasibility of onboard carbon capture continues to be demonstrated, several challenges remain before widespread adoption becomes practical.
The regulatory framework is still evolving, with the International Maritime Organization (IMO) only beginning to develop comprehensive protocols for OCCS systems . Standardized safety procedures, emissions accounting methodologies, and certification processes must be established to ensure consistent implementation across the global fleet.
Infrastructure development represents another critical challenge. As Edvin Endresen, CEO of Solvang ASA, notes: "CO2 can be recycled and used in land-based industries, but the global infrastructure for discharge for shipping needs to be developed fast" 9 . Ports worldwide will need to invest in CO2 offloading facilities, intermediate storage, and transportation networks.
Perhaps most importantly, the business case for carbon capture must continue to strengthen. Currently, the technology requires significant investment—approximately $10 million per vessel for retrofits 8 . However, this compares favorably against the $15-25 million required for methanol conversion or the over $30 million needed for ammonia adaptation.
Additionally, captured high-purity CO2 can generate revenue of $200-500 per metric ton depending on the application, creating potential annual returns of up to $8 million for large container vessels 8 .
The emergence of cross-border carbon transport and storage projects, such as Norway's Northern Lights initiative—which began operations in 2025 and will store imported CO2 from the Netherlands and Denmark—creates essential infrastructure for permanent carbon sequestration 2 . Such projects demonstrate that the complete value chain from capture to storage is becoming commercially viable.
| Transport Method | Pressure Level | Current Ship Capacity | Key Challenges | Development Status |
|---|---|---|---|---|
| Low Pressure (LP) | Near triple point (-56.6°C at 0.52 MPa) 3 | 23,000-50,000 m³ class designs 3 | Requires extreme cooling; dry ice formation risk 3 | Approval in Principle obtained for large-scale designs 3 |
| Medium Pressure (MP) | Higher pressure, moderate cooling | Less than 10,000 m³ 3 | Tank reinforcement needs limit scaling 3 | Currently operational in small ships 3 |
| Elevated Pressure (EP) | High pressure, minimal cooling | 40,000 m³ class under study 3 | Specialized slender cylinder tanks required 3 | Demonstration phase; proprietary KNCC system 3 |
The rapid advancement of carbon capture, solidification, and storage technology aboard ships represents more than just a technical achievement—it signals a fundamental shift in how we conceptualize maritime emissions.
What was once considered an unavoidable byproduct of global trade is now being reimagined as a manageable resource. From the historical first full-scale installation on the Clipper Eris to the groundbreaking ship-to-ship transfer in Shanghai, each milestone demonstrates that decarbonizing shipping is not only necessary but increasingly practical.
The journey toward widespread adoption continues, with important work ahead in standardizing regulations, building infrastructure, and optimizing economics. Yet the progress to date offers compelling evidence that carbon capture technology, particularly solidification approaches, will play a crucial role in shipping's decarbonization pathway.
As these systems become more sophisticated and widespread, we may soon regard today's pioneering vessels as the beginning of a revolution that transformed shipping from a carbon source to part of the climate solution.
"The introduction of carbon capture and storage capabilities on board represents a major leap forward for maritime sustainability. It represents a system change that has been made possible by close collaboration between our companies."
This spirit of collaboration—between shipowners, technology providers, regulators, and researchers—will be essential as the industry navigates the challenging but promising waters toward a carbon-neutral future.